1. Field of the Invention
The present invention relates to an optical modulation device having an electrooptical device, such as a liquid crystal panel, and to a projection display device using this optical modulation device.
2. Description of the Related Art
A liquid crystal panel that serves as an electrooptical device for use in a projection display device generally comprises an active matrix substrate having pixel electrodes and pixel switching elements, an opposite substrate having opposite electrodes, and liquid crystal interposed between the active matrix substrate and the opposite substrate. The liquid crystal is filled in a region partitioned by a sealing layer out of the space between the active matrix substrate and the opposite substrate, and the alignment state thereof is controlled pixel by pixel between the active matrix substrate and the opposite substrate.
Therefore, in a projection display device using the liquid crystal panel having such a structure as an optical modulation device, light emitted from a light source is collected and guided to the liquid crystal panel by a light-collecting optical system, and this light is optically modulated by the liquid crystal, whereby a predetermined image is enlarged and projected onto a projection plane, such as a screen, by a projection lens.
The liquid crystal panel structured as mentioned above is usually held by a light-shielding holding member having an open portion corresponding to an image area. In general, the image area is outlined by a light shielding portion of Cr (chrome) that is formed between the active matrix substrate and the opposite substrate to define the periphery.
On the light-incident side of the liquid crystal panel, however, since a cover portion that forms a peripheral edge of the open portion of the holding member faces the light-incident surface of the liquid crystal panel (opposite substrate) and overlaps with the light-shielding portion in a planar manner, light that is incident from the outside of the inner peripheral edge of the cover portion is blocked by the cover portion depending on the incident angle. Therefore, the peripheral portion of a projection image becomes dark, and this may deteriorate the quality of the projection image.
An object of the present invention is to provide an optical modulation device that is able to improve the quality of a projection image, and a projection display device using this optical modulation device.
An optical modulation device of the present invention includes an electrooptical device having a first light-transmissive substrate disposed on the light-incident side, a second light-transmissive substrate disposed on the light-emitting side, liquid crystal interposed between opposing surfaces of these first and second light-transmissive substrates, and a driving circuit disposed at the peripheral edge of a light-incident surface of the second light-transmissive substrate, and a holding member for holding the electrooptical device, wherein a first light-shielding portion for defining an image area is formed between the first and second light-transmissive substrates in the electrooptical device, a cover portion for covering the peripheral edge of a light-incident surface of the first light-transmissive substrate is formed in the holding member, and Wp and W1 are set in a relationship that is expressed by the following equation (1):
Wp less than W1xe2x80x83xe2x80x83(1)
where Wp is the distance from the end of the first light-transmissive substrate to the inner peripheral edge of the cover portion in the holding member, and W1 is the distance from the end of the first light-transmissive substrate to the inner peripheral edge of the first light-shielding portion.
Herein, xe2x80x9cthe inner peripheral edge of the cover portionxe2x80x9d means a part of the cover portion that projects toward the image area to the largest degree and that is most apart from the light-incident surface of the first light-transmissive substrate. Furthermore, xe2x80x9cthe distance from the end of the first light-transmissive substratexe2x80x9d means the distance along the in-plane direction of the first light-transmissive substrate.
In the present invention configured like this, since the distance Wp from the end of the first light-transmissive substrate to the inner peripheral edge of the cover portion is set to be smaller than the distance W1 from the end of the first light-transmissive substrate to the inner peripheral edge of the first light-shielding portion, there is no fear that the inner peripheral edge of the cover portion may project into the image area beyond the first light-shielding portion. Since incident light that is incident from the outside of the inner peripheral edge of the cover portion reliably enters the entire image area without being blocked by the cover portion, the peripheral portion of a projection image does not become dark, and the quality of the projection image is thereby improved.
In the optical modulation device of the present invention, when the incident angle of incident light, which is incident from the inside of the inner peripheral edge of the cover portion, of light that is incident on the electrooptical device, is xcex8i, the incident angle of incident light, which is incident from the outside of the inner peripheral edge of the cover portion, is xcex8o, the distance from the inner peripheral edge of the cover portion to the light-incident surface of the first light-transmissive substrate is dp, the thickness of the first light-transmissive substrate is d1, the distance from the end of the first light-transmissive substrate to the outer peripheral edge of the first light-shielding portion is W1xe2x80x2, and the refractive index of the first light-transmissive substrate is n1, it is preferable to set Wp, W1, and W1xe2x80x2 in a relationship expressed by the following equation (2).                                           W1            xe2x80x2                    +                      dp            ⁢                          xe2x80x83                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                    +                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        Wp        ≤                  W1          -                      dp            ⁢                          xe2x80x83                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                    -                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        2        )            
When the first light-transmissive substrate and the second light-transmissive substrate are bonded with a sealing material of an ultraviolet-curing type, there is a need to leave a light-transmissive portion of the first light-transmissive substrate outside the first light-shielding portion. Since the first light-transmissive substrate has the thickness d1, incident light that is incident from the inside of the inner peripheral edge of the cover portion is, in some cases, not entirely blocked by the cover portion of the holding member according to the incident angle, passes through the light-transmissive portion of the first light-transmissive substrate, and leaks from the outer peripheral edge of the first light-shielding portion. For this reason, the leaking incident light impinges on a driving circuit that is disposed on the periphery of the second light-transmissive substrate, thereby causing a malfunction of the driving circuit. When the distance Wp is set within the range given by the equation (2), however, there is no fear that the quality of a projection image may be deteriorated by incident light that is incident from the outside at the incident angle xcex8o. Moreover, there is no fear that incident light incident from the inside at the incident angle xcex8i may leak from the outer peripheral edge of the first light-shielding portion, and that the light may be applied onto the driving circuit disposed on the periphery of the second light-transmissive substrate. Therefore, even when a light-transmissive portion is formed outside the first light-shielding portion, the driving circuit is prevented from malfunctioning.
Furthermore, in the optical modulation device of the present invention, it is preferable to form a third light-transmissive substrate between the first light-transmissive substrate and the cover portion. Furthermore, when the incident angle of incident light incident from the inside of the inner peripheral edge of the cover portion, of light incident on the electrooptical device, is xcex8i, the incident angle of incident light incident from the outside of the inner peripheral edge of the cover portion is xcex8o, the distance from the inner peripheral edge of the cover portion to a light-incident surface of the third light-transmissive substrate is dpxe2x80x2, the thickness of the first light-transmissive substrate is d1, the thickness of the third light-transmissive substrate is d2, the distance from the end of the first light-transmissive substrate to the outer peripheral edge of the first light-shielding portion is W1xe2x80x2, and the refractive indices of the first light-transmissive substrate and the third light-transmissive substrate are n1 and n2 respectively, it is preferable to set Wp, W1, and W1xe2x80x2 in a relationship expressed by the following equation (3).                                           W1            xe2x80x2                    +                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                    +                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                +                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        Wp        ≤                  W1          -                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                    -                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                -                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        3        )            
In such a case, the third light-transmissive substrate serves as a dustproof light-transmissive substrate, so that the light-incident surface of the first light-transmissive substrate is protected from dust and flaws, and there is no fear that such dust and flaws will be enlarged in projection.
In this case, it is preferable to form a second light-shielding portion between the third light-transmissive substrate and the first light-transmissive substrate and to set Wp, W1, and W2 in a relationship expressed by the following equation (4):
Wp less than W2 less than W1xe2x80x83xe2x80x83(4)
where W2 is the distance from the end of the first light-transmissive substrate to the inner peripheral edge of the second light-shielding portion.
In such a case, since the second light-shielding portion is formed between the first light-transmissive substrate and the third light-transmissive substrate and the distance W2 from the end of the first light-transmissive substrate to the inner peripheral edge of the second light-shielding portion is set within the range given by the equation (4), light that is incident from the inside and passes through the inner peripheral edge of the cover portion is blocked by the second light-shielding portion. Therefore, in the case of the first light-shielding portion, there is no need to consider such incident light. Regarding light that is incident from the inside, consideration should be given to incident light that passes through the inner peripheral edge of the second light-shielding portion, so that the distance W1xe2x80x2 from the end of the first light-transmissive substrate to the outer peripheral edge of the first light-shielding portion is set to be larger.
When the distance from the end of the first light-transmissive substrate to the outer peripheral edge of the second light-shielding portion is W2xe2x80x2, Wp, W1, W1xe2x80x2, W2, and W2xe2x80x2 may be set in a relationship expressed by the following equations (5) and (6).                                           W2            xe2x80x2                    +                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                    +                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        Wp        ≤                  W2          -                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                    -                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        5        )                                                      W1            xe2x80x2                    +                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        W2        ≤                  W1          -                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        6        )            
In such a case, the distance W2xe2x80x2 from the end of the first light-transmissive substrate to the outer peripheral edge of the second light-shielding portion can be set based on a positional relationship to the distance Wp of the cover portion so that light incident from the inside does not leak from the outer peripheral edge of the second light-shielding portion. Therefore, under certain circumstances, the second light-shielding portion may be formed over a wide area from the end of the first light-transmissive substrate by setting W2xe2x80x2 to be at zero, whereby the incident light from the inside is less prone to leak toward the driving circuit.
When an air layer having a thickness d3 is formed between the first light-transmissive substrate and the third light-transmissive substrate, and a second light-shielding portion is formed on the light-emitting surface of the third light-transmissive substrate, it is preferable to set Wp, W1, W1xe2x80x2, W2, and W2xe2x80x2 in a relationship expressed by the following equations (7) and (8).                                           W2            xe2x80x2                    +                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                    +                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        Wp        ≤                  W2          -                                    dp              xe2x80x2                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                    -                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        7        )                                                      W1            xe2x80x2                    +                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                +                      d3            ⁢                          xe2x80x83                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                          ≤        W2        ≤                  W1          -                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                -                      d3            ⁢                          xe2x80x83                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                                              (        8        )            
In such a case, since the air layer is formed between the first light-transmissive substrate and the third light-transmissive substrate, heat that is generated in the third light-transmissive substrate is less prone to be transmitted toward the electrooptical device, compared with a case in which the air layer is not formed.
In contrast, when the second light-shielding portion is formed on the light-incident surface of the first light-transmissive substrate, it is preferable to set Wp, W1, W1xe2x80x2, W2, and W2xe2x80x2 in a relationship expressed by the following equations (9) and (10).                                           W2            xe2x80x2                    +                                    (                                                dp                  xe2x80x2                                +                d3                            )                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            i                    +                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        Wp        ≤                  W2          -                                    (                                                dp                  xe2x80x2                                +                d3                            )                        ⁢            tan            ⁢                          xe2x80x83                        ⁢            θ            ⁢                          xe2x80x83                        ⁢            o                    -                      d2            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n2                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        9        )                                                      W1            xe2x80x2                    +                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      i                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    i                                                                                      ≤        W2        ≤                  W1          -                      d1            ⁢                          xe2x80x83                        ⁢                                                                                                      sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                      ⁢                                              xe2x80x83                                            ⁢                      o                                                                                                                                        n1                    2                                    -                                                            sin                      2                                        ⁢                    θ                    ⁢                                          xe2x80x83                                        ⁢                    o                                                                                                          (        10        )            
In this case, the aforesaid effect produced by forming the air layer is also obtained.
On the other hand, a projection display device of the present invention includes a light source, the optical modulation device mentioned above, and a projection lens for projecting light modulated by the optical modulation device. It is possible to provide a projection display device in which the above-mentioned effects are similarly obtained.